A framework like this is especially suitable to be modeled using multi-event modelling in E-SURGE as E. Cooch mentioned. This is the section of analysis help in MARK and I hope not to go off-topic in my answer, this is just to help you to figure out a bit more how it would work in E-SURGE. The main advantage would be that you do not loose information by having to consider a third group made of unknown sex individuals.
In your case, if you have no mis-classification (female wrongly assigned to male and vice versa) you would have three states (female alive, male alive, dead) and four events (0, not detected, 1 detected assessed as female, 2 detected assessed as male, 3 detected without sex assessment).
You will have to define your probabilistic matrices in GEPAT (see*). In the GEPAT syntax a letter, any, means the parameter/probability you want to get estimated, an "*" is the probability of the complementary event (i.e. 1-p), and a "_" means you know that probability is zero. In your case you would have:
INITIAL STATE (one single step)
Initial State (two columns: fem, mal)
* p
TRANSITION (one single step)
Survival (3 rows and 3 columns: fem, mal, dead)
s _ *
_ s *
_ _ *
EVENT (two steps)
Encounter (3 rows: fem, mal, dead; 3 columns: non-detected, female detected, male detected)
* p _
* _ p
* _ _
Sex Assessment (3 rows: non-detected, female detected, male detected; 4 columns: 0, 1, 2, 3)
* _ _ _
_ d _ *
_ _ d *
Note you can put any letter in the matrix (its position determines the parameter you want to be estimated), it is arbitrary.
There are good references (e.g. **;***) with good supplementary material you may want to see if you decide to use this approach. In that case, you may find extra help in the E-SURGE Phidot section.
*
https://www.cefe.cnrs.fr/images/stories ... MANUAL.pdf** Pradel, R., Maurin‐Bernier, L., Gimenez, O., Genovart, M., Choquet, R., & Oro, D. (2008). Estimation of sex‐specific survival with uncertainty in sex assessment. Canadian Journal of Statistics, 36(1), 29-42.
*** Genovart, M., Pradel, R., & Oro, D. (2012). Exploiting uncertain ecological fieldwork data with multi‐event capture–recapture modelling: an example with bird sex assignment. Journal of animal ecology, 81(5), 970-977.